Synthesis and radiopharmacological evaluation of 2′-(4-fluorophenyl)-21-[18F]fluoro-20-oxo-11β,17α-dihydroxy-pregn-4-eno[3,2-c]pyrazole as potential glucocorticoid receptor ligand for positron emission tomography (PET)

The radiosynthesis and the radiopharmacological evaluation of pyrazolo steroid 2′-(4-fluorophenyl)-21-[18F]fluoro-20-oxo-11β,17α-dihydroxy-pregn-4-eno[3,2-c]pyrazole [18F]-2 is described. The radiolabeling was accomplished in 3–4% decay-corrected radiochemical yield within 80 min at an specific radioactivity of 0.8–1.2 Ci/μmol. Biodistribution studies in male Wistar rats showed an initial brain uptake of 0.25 ± 0.03% ID/g after 5 min, which remained constant over 60 min. The radiopharmacological evaluation of compound [18F]-2 was completed with autoradiography using rat brain sections and micro-PET imaging.